The present invention relates to a scroll type compressor for use in an air-conditioning system for a vehicle.
Conventionally, a scroll type compressor includes a housing, a fixed scroll member and a movable scroll member. The fixed scroll member is fixed in the hosing and has a fixed bass plate and a fixed spiral wall. The movable scroll member has a movable base plate and a movable spiral wall that is engaged with the fixed spiral wall of the fixed scroll member. A compression chamber defined between the fixed and movable spiral walls is gradually reduced in volume as refrigerant gas in the compression chamber is gradually compressed and is moved toward a center side of the spiral walls by orbital movement of the movable scroll member. Therefore, the refrigerant gas is compressed.
There is a scroll type compressor in which a ring is interposed between the housing and the movable base plate of the movable scroll member to urge the movable scroll member towards the fixed scroll member, in order to enhance the sealing of the compression chamber against compression reactive force applied to the movable scroll member in an axial direction of a rotary shaft of the compressor (e.g. column [0036] and FIG. 8 in Japanese Unexamined Patent Publication No. 8-219063).
Namely, a receiving wall is formed in the housing so as to receive the compression reactive force from a back surface of the movable base plate of the movable scroll member in the axial direction of the rotary shaft. The ring is interposed between the receiving wall and the movable base plate of the movable scroll member. A part of an annular and planar body of the ring is bent, thereby the shape of the cross section around the bent portion of the ring is formed so as to function as a spring. The spring-shaped portion of the ring is elastically interposed between the receiving wall and the movable base plate of the movable scroll member.
Therefore, dimensional tolerances of the movable and fixed scroll members in the axial direction of the rotary shaft are absorbed by elastic deformation of the spring-shaped portion of the ring. It is unnecessary to adjust the cam between the fixed and movable scroll members in the axial direction of the rotary shaft when the scroll type compressor is assembled.
However, it takes labor hour to change the shape of the cross-section of the ring so as to function as a spring. Also, even if the shape of the spring-shaped portion of the ring is slightly different from a desired shape, the force to urge the movable scroll member is varied relatively. Therefore, in order to cope with the securement of the sealing of the compression chamber and the suppression of the sliding resists between the fixed and movable scroll members, it is necessary to manufacture the spring-shaped portion with a high degree of accuracy. These things cause high cost of the scroll type compressor.